The present invention relates generally to control rods used in aircraft actuator systems and more particularly to providing instrumented control rods.
Actuator systems are used within an aircraft to transmit a pilot""s control inputs from controls in a cockpit to control surfaces on the exterior of the aircraft such as ailerons and rudders. In some actuator systems, the amount of force exerted by the pilot to the control in the cockpit is directly proportional to the amount of force required to operate the control surface. The amount of force applied by a pilot to a control is indicative of many things. For example, if a pilot must increase the amount of force applied to a control to operate a control surface, it may mean that a component of the actuator system linked to the control or the control surface itself is not working properly or has failed. Therefore, it would be useful to know how much force is being transferred between components within an actuator system in order to diagnose the actuator system during operation of the actuator system. More particularly, it would be beneficial to record the amount of force transferred between components in an actuator system in a flight recorder to help in diagnosing problems with actuator systems and control surfaces.
Putting force sensing and reporting components into an actuator system is difficult. In existing systems, there simply may not be enough space to accommodate a new component without completely restructuring the aircraft containing the actuator system. Even if the physical space is available for a new component, there may be significant amounts of EMF emissions in the area making the choice of sensing and reporting components difficult. Additionally, the only available space may have extreme thermal or environmental conditions that may cause premature failure of an exposed and sensitive measurement system. In new actuator systems, the introduction of a new component into an existing actuator system design may require a series of expensive design iterations where many different components within an aircraft are redesigned to accommodate the new component.
Therefore, a need exists for a method to integrate force sensing and recording components into existing and newly designed actuator systems in an unobtrusive and cost effective way. Preferably the integration method should be adaptable to many different kinds of actuator systems and not unduly increase the overall weight of the actuator system. The present invention meets such need.
A force sensor rod useful as a control rod in an aircraft actuator system is provided by the present invention. The force sensor rod is constructed from a tube and a force sensing transducer such as a load cell. The force sensing transducer has a body containing a force responsive primary element and the force responsive primary element""s associated electronic circuitry. The force sensing transducer is provided with a protruding end composed of a material relatively harder than the tube material. The threads on the protruding end preferably terminate in a plurality of axially spaced grooves adjacent to the force sensing transducer body and normal to the axis of the force sensing transducer. The tube is threaded onto the protruding end of the force sensing transducer and swaged onto the protruding end by causing the tube material to flow into the grooves.
In one embodiment, the force sensing transducer includes a cable extending from the protruding end and the cable is routed through the tube.
In another embodiment, a second protruding end is provided. The second protruding end is bored and tapped creating a female threaded connection for a rod end. Alternatively, the second protruding end is threaded providing a male threaded connection for a rod end.
The force sensor rod is readily incorporated into an aircraft actuator system. The force sensor rod is operably coupled between two components of an actuator system. The force sensing transducer is connected to a signal conditioning module containing a power supply and a signal conditioner. The signal conditioning module supplies excitation power for the force sensing transducer and signal conditioning for an output signal from the force sensing transducer. The conditioned output signal is provided to a flight recorder for recording.
An advantage of a preferred force sensor rod is that it has a form factor similar to a conventional control rod making it suitable to retrofit existing actuator systems and easy to design into new actuator systems. Furthermore, the force sensor rod is easily adapted to different control rod ends without extensive modifications.
An additional advantage of a preferred force sensor rod is that the components are threaded and then swaged together creating a permanent and secure connection that does not require additional lock nuts or other kinds of connection locking mechanisms. This creates a lightweight and sleek design suitable for use in an aircraft.
A further advantage of a preferred force sensor rod is that the force sensing transducer is coupled to the tube with a swaged connection creating a hermetically sealed enclosure protecting the cable exiting the force sensing transducer. This adapts the force sensing transducer for use in hostile environments where solvents, hydraulic fluids, and corrosive liquids are used. Furthermore, routing the cable through the tube provides electrical shielding and mechanical protection as well.